Handheld surveillance and weapon mounted sights are well known, and typically include a number of lens elements arranged to focus light from a scene viewed by a user via an eyepiece of the sight. Such sights often include image intensifier arrangements to increase the intensity of available light in the optical system to permit use of the sight in low-light conditions such as at night, or for conversion of non-visible light sources such as infrared.
However, previously proposed sights of the type described above suffer from significant disadvantages when used in the field, which can adversely affect their usefulness in real world conditions. For example, the image intensifier components may be more sensitive to shock and/or vibration than other components of the weapon sight, and may be damaged in the course of operation of the weapon, for example, by recoil from discharge of a firearm.
An image intensifier tube is a device that intensifies (or amplifies) low light level images to levels that can be seen with the human eye or detected by digital image sensors. In general, image intensifier tubes include a photocathode, a micro-channel plate (MCP), and a phosphor screen. Image intensifier tubes may collect the existing ambient light through the objective lens of the night vision device. The light may originate from natural sources, such as starlight or moonlight, or from artificial sources such as streetlights or infrared illuminators. The low level of incoming light, which consists of photons, enters the tube through an input window and strikes the photocathode. The photocathode is generally a very thin light sensitive layer deposited on the inside of an image intensifier input window that converts the photons into electrons and releases them into the vacuum of the tube. Image intensifier tubes generally operate under a vacuum, for example, of about 10-9 to 10-10 torrs, which protects the photocathode from oxidation and rapid destruction. Once released by the photocathode, these photo-electrons are accelerated and focused by a high electrical field towards the MCP. The MCP is generally a thin glass disc, for example, less than half a millimeter thick. The MCP produces a large number of secondary electrons for each received electron, which are accelerated toward the phosphor screen. One or more of these components may be damaged when an image intensifier tube is mounted to a weapon.
FIG. 1 shows an exemplary prior art mounting arrangement of an image intensifying tube 110. A sight 180 is mounted to a weapon 190 via sight mounts 185. The image intensifying tube 110 is directly mounted to the sight 180 by direct contact means, for example, by a threaded mount, or other similar attachment means. When the weapon 190 is discharged or otherwise subject to shock, impact, or vibration, the force is transmitted from the weapon 190 through the sight mounts 185 and the sight 180 to the image intensifying tube 110, potentially causing damage to the image intensifying tube 110.
Previous shock isolation solutions using padding, for example, elastomer pads, have suffered from several shortcomings, such as reduction in performance over time, non-linear impact response, degradation due to thermal conditions, movement during temperature excursions, and failure to return to original shape after deformation. Therefore, there is a need in the art to address the abovementioned shortcomings.